Dry battery



F. MVaCCALLUM Jan. 17, 1939.

DRY BATTERY Filed Jan. 22, v1937 FIC-3.2.v

Patented Jan. 17, 1939` UNITED? STATES DRY BATTERY Frank MacCallum,'Washwood Heath, Birmingham, England, assignor to Maxolite HoldingsLimited, Kingsway, London, England Application January 2.2, 1937, SerialNo. 121,891 In Great Britain April 18, 1935 7 Claims.

'Ihis invention relates to dry batteries of the kind comprising a numberof zinc plates assembled together with carbon, electrolyte anddepolarizer elements arranged sandwichwise.

It is common practice in dry batteries of the kind specified to assemble'the elements of one or more cells sandwichwise and to bind the elementstogether by a coating or casing of wax, paraffin or the like, extendingaround the edges of the assembly and over the marginal portion of theouter plates or faces of the assembly, this coating or casing alsosealing the edges of the assembled cell or cells.

The present invention, however, concerns the provision of a protectingcoating around'the marginaledges of one or'both surfaces of the carbonzinc element prior to the assembly of the battery, the object of theinvention being to provide for improved electrical isolation betweencell and cell in a battery of the kind speciiled.

Referring to the drawing:-

Figure l shows in section a battery incorporating the present invention.

Figure 2 shows to an enlarged scale, a portion of same.

Figure 3 is a perspective view oi one plate of the battery shown inFigure l.

Figure 4 is a section of a portion of a slightly modified construction,

Flgures to 8 show in section further alternatives according to thisinvention.

In Figure 1 is shown a dry battery comprising a number oi zinc plates lassembled together with depolarizer and electrolyte elements iltherebetween, the two intermediate plates each having on one face acarbonaceous coating l2 comprising carbon particles in a suitableadhesivecarrier and having on the other face a sheet i3 impregnated withelectrolyte.

The end plate l@ has a carbon coating l2 on the inwardly vdirected faceand the other end plate i5 has an electrolyte impregnated sheet i3 onits inwardly directed face. Thus, in the construction illustrated, thebattery comprises three complete cells but any number of cells may beprovided by adding elements il and duplex zincv and carbon plates t it.

The battery is enclosed in a casing I6 and sealy ing material il and theterminals or conductors4 ware suitably ilxed to the end plates I4 and i5and extend through the sealing material il. Prior to the assembly of thebattery, the marginal portion of each carbon zinc element I0, i4,-

is provided with an adhering coating I9 of electrically insulatingmaterial for the purpose of in- 35 parts by weight (Cl. 13G-111)sulatlng the electrolyte of one cell from the carbon of the next cell.

Theinsulating coating lil is applied to that portion of the carbon sidewhich is left uncovered by the depolarizer tablet when the battery isas- 5 sembld, this' coating extending over the marginal portion of theplate and the outer face of the pressed-up edges 29.'

The carbon coating l 2 is then applied and overlaps the edges of thecoating i9 which insulates l0 the carbonaceous coating -i2 from the nextcell vof the `battery and also forms a seating for the sealing materialwhich is subsequently applied. The essential properties of the coatingI9 arez- 1 'l 'l ld (l) It must form a flux for the sealing materialilwhich is subsequently applied so that this sealing material will flowreadily over the entire marginal portions of the plates i9, it and i9and form an effective seal with such marginal portions.

(2) It is required to form a delayed solvent for the adhesive carrier inthe carbonaceous coating so vthat the coating i9 marries up with thecarbonaceous coating i2 to vform an edective seal at 25 the junctionbetween these two coatings. It

must not, however, have a damaging solvent efect on the coating i2 andmusty not unduly soften when the hot sealing material il is applied, butmust soften sumclentiy on its surface to become an integral part of thesealing il when cooled.

(3) it is preferably brushable and is required to form a non-conductingseal over the marginal portions of the plates i9, ld and i5 to insulatethe carbonaceous coating of one cell from the next cell of the battery.

(4) Itmust be chemical and water-proof and capable of adhering closelytothe carbon-zinc element.

The preferred sealing material which has been 4Q found to meet all theserequirements is prepared from the following constituents:-

parts by weight of the synthetic resin commercially marketed under thetrade nameAl i5 bertol HIL".

2 parts by weight of chlorinated rubber as marketed commercially underthe trade name Tegaphon.

linseed stand oil, and

50 lparte. by weight of xylol spirit.

The constituents are mixed together according to the following method:-

The chlorinated. rubber is slowly dissolved in of about 160 F.

The remaining linseed stand oil is cooked at about 400 F. with theAlbertol until a complete intimatemixture is obtained. 'I'his liquid isthen cooled-to about 200"4 F. and the mixture of chlorihated rubber andlinseed oil is stirred in until the whole is thoroughly mixed, afterwhich the material is cooled to normal temperature and the xylol spiritadded to produce a working or brush'- ing varnish.

Any digested rubber could be used in place of the chlorinated rubberabove referred to but this latter is preferred in. that it can beobtained in granular form and is particularly suitable for use in thisparticular application.

The coating material is a delayed solvent for the carrier in thecarbonaceous coating so that when the two coatings l2 and is are appliedand overlapped at the junction therebetween, the two coatings dissolvepartially one in the other and unite to form a complete' seal over thejunction between the two coatings.

The chlorinated rubber in the coating i9 delays the solvent action onthe carrier in the carbon coating so as to limit this solvent action andprevent complete softening of the carbonaceous coating in an undesirablemanner.

The chlorinated rubber constituent cannot be easily re-dissolved afterit has once hardened and this constituent renders the coating i9 capableof resisting the uxing action to some extent.

The chlorinated rubber does not dissolve in the synthetic resin but thelinseed oil is a solvent both for the synthetic resin and for thechlorinated rubber and is compatible with both of these materials.

The synthetic resin marketed under the trade name Albertol also includesa certain amount of linseed oil and thus readily combines with theremaining constituents.

The sealing material il has to be applied hot and unless the coating i9is formed from material capable of withstanding the action of this hotsealing il, dii'licuities wquld be introduced due to softening of thesealing coating le with possible lifting of this coating from the zincplate.

The combination of materials above specied provides a sealingcoating i9which will withstand the temperature conditions due to the applicationof the hot sealing il and no difficulty is experienced due to lifting orsoftening of the coating i9 as might be the case if a simple varnish orwax-like material was used for this coating i9.

Due to the chlorinated rubber constituent the coating i9 does not softento the extent that an ordinary varnish or wax-like coating would, but itforms a ux for the sealing material il which thus ows readily over thecoating i9 and effectively seals the entire marginal portion of thevzinc plates. i

The sealing compound l1 may be formed from the constituents abovespecified for the coating i9 but preferably includes slightly more oiland melts at a slightly lower temperature than the coating I9 to preventcomplete softening of this coating i9 when the sealing Il is appliedhot.

In Figures l to 3 the-insulating coating is shown as applied to theedges and to one side of the plate, i. e. that side which is to becoated with the carbonaceous coating, but the insulating material isapplied only at the marginal portions of the surface near the edges ofthe element in the form of a border.

In this construction the insulating material I9 y 2,144,574 20parts ofthe linseedstandv'oil at'a temperature is applied before thelcarbonaceous coating I2 is applied to the zinc and an area of cleanzinc is left within at the centre of the plate so that the carboncoating subsequently applied will make good and direct contact with thezinc at the bare portion in the centre of the plate and will overlap theinsulating material by an appreciable amount, but will not extend to theedges of the plate.

In the modification shown in Figure 4, the carbon coating i2 is appliedrst, but its application is confined to an area smaller than the wholearea of the plate, leaving a margin or border at and near the edgeswhich are subsequently coated with the insulating material i9.

If theV carbon coating extends right to the boundaries of the coatedface of the zinc plate, it

may only be necessary to coat the edges of the plate with insulatingmaterial i9, since the material is is particularly required at the edgesof the carbon coating where both carbon and exposed zinc are adjacentone another, and where a small local cell would be set up if anyelectrolyte reached this position by leakage or otherwise. By providinga coating I9 at or over the junction between the carbon vcoating and theadjacent exposed zinc, the possibility of such local action is reducedor eliminated.

With the object of assisting in the securing of proper electricalisolation between cell and cell, the edges 2li of the plates are turnedup so that each plate is formed into a shallow tray and the coating i9is extended over at least one surface of such edges 2Q. This methodprovides amechanical barrier tc the encroachment of the electrolyte onone side of the zinc plate i0 to the carbon coating l2 on the oppositeside of the zinc plate.

Further, such a construction extends the length of the path or gapbetween the electrolyte and the carbon, but without in any wayincreasing the size of the battery.

"This method of construction also has the advantage that it providesgreater stability or stiliness in the zinc plate.

In addition, the turned up edges of the zinc plate serve to. positionand locate both the depolarizer tablet and the electrolyte tablet orpaste, and provide for bothquicker and more accurate assembly of thecells.

Further, with the object of improving the sealing of the edges of thecells, theborder of the electrolyte tablet may be kept in a dry stateand free from electrolyte paste-with the object of allowing the sealingor binding material, which is subsequently applied to the edges of thebattery, to assist in forming the insulating barrier between the carbonon the one side of the plate and the electrolyte on the other side, andalso to permit of easier handling of the elements during assembly, andprovides the 'necessary factors of cleanliness and safety during theprocesses of manufacture.

The sealing fluids are poured in when the pack of cells is in a paperbag or container, and in order to allow the sealing material i1 to flowaround between theback of the end plates and the container, each endplate is spaced away from the end of the container by a piece oflpacking 2i, such as cardboard,placed against the outer side of the plateand stuck thereto, the packing material being set back from the edge ofthe plate.:

one surface of a ilat zinc plate 22 prior to the application-thereto ofthe carbon coating.

In Figure 6 the coating I9 extends over the edge and marginal portion ofboth faces of the zinc plate.

In'Figure '7 the coating I9 is applied to the marginal portiononly ofone face of the plate -whilst in Figure 8 the coating is applied to themarginal portion of both surfaces but not to the edge of the plate.

The essence of the. design of the battery is that a prescribed spacemust be available for sealing the edges of the cells, so that theelectrolyte of one cell is efdoiently insulated from the carbon of thenext cell, and also to assist in pre-A venting the formation of internalcells at the edges, and this is accomplished by means set out herein,and further by the insetting of the depolarizer tablet from the edges ofthe zinc.

What I claim then iszv 1. A carbon zinc element for use in the con'-struction of a dry cell or battery comprising a zinc plate, an adheringcoating of electrically in# sulating material applied to edge portionsof said zinc plate, a thin carbonaceous liquid-prooi layer adhering toone side of said plate, both of said coatings being applied to said zincplate prior to assembly ofthe plate in the cell or battery and saidcoating of insulating material and said car# bonaceous layer overlappingone another so as to form an insulating seal atthe junction between theplate and the peripheral edges of the carbonaceous layer. f

2. A carbon zinc element for use in thereonstruction of a dry cell orbattery comprising a zinc plate, athin carbonaceous liquid-proof layeradhering to the centre part of one side of said plate leaving a marginfree from said layer near the edge of said plate and an adhering coatingoi electrically insulating material applied 'Y to said margin prior toassembly 'of the plate in the cell or battery to form a non-conductingseal at such edge portions and to form a flux for sealing materialsubsequently applied, said coating of insulating material and saidcarbonaceous layer overlapping'one another so as to seal the junctionbetween said plate and the peripheral edges of said carbonaceous layer.

3. A carbon zinc element for use in the construction of a dry cell orbattery comprising a zinc plate, a thin carbonaceous liquidproof layeradhering to the centre part of one side of said plate leaving a marginfree from said layer near the edge of said plate. an adhering coatingoi' electrically insulating material applied to said margin prior toassembly of the plate in the cell or battery to form a non-conductingseal at such edge portions and to form a flux for sealing materialsubsequently applied and said carbonaceous layer overlapping the innerperipheral edges of said marginal coating.

4. In a flat type dry cell battery a depolarizer mix, a carbon electrodein contact with one side of said mix, an electrolyte and a zinc plate atthe other side of said mix, said carbon electrode comprising a thincarbonaceous liquid-proof layer adhering to said plate, edge portions ofsaid plate free from said carbonaceous layer. and an adher- 'mingcoatingotelectricallyinsulatingmaterialapmix, a carbon electrode incontact with one side plied to said `edge portions of said zic plateprior form an insulating seal at the junction between 5 e the plate andthe peripheral edges of the carbonaceous layer and to form a iux forsealing material subsequently applied.

5. In a ilat type 'dry'cell battery a. depolarizer 10 of said mix, anelectrolyte and a zinc plate at the other side oi said mix, saidcarbonelectrode comprising a thin carbonaceous liquid-proof layeradhering to the centre part of one side of said plate, an adheringcoating of electrically insulating material, applied to the edges and tomarginal portions of both surfaces of said zinc plate, both saidcarbonaceous layer and said insulating coating being applied to saidplate prior to assembly of the plate in the cell or battery, saidinsulating coating adhering directly to said edgesand marginal portionsof the zinc plate to form a nonconducting seal at such edge portions andto form a ux for sealing material subsequently applied, said coating ofinsulating material and said carbonaceous layer overlapping one anotherso as to seal the junction between said plate and the peripheral edgesof said carbonaceous layer.

6. In a flat type dry cell battery a depolarizer mix, a carbon electrodein contact with one side of said mix, an electrolyte anda zinc plateatthe other side of said mix, said carbon electrode comprising a thincarbonaceous liquid-proof layer adhering to the centre part oi one sideof said plate, edge portions of said plate free from said 35carbonaceous layer, an adhering coating ofelectrically insulatingmaterial applied to said edge portions and covering the peripheralportions of the carbonaceous layer, said insulating layer being appliedprior to assembly oi'the plate in the cell or battery and adheringdirectly to said edge lportions of the plate to form a non-conductingseal at such edge portions and to forma flux for sealing materialsubsequently applied, said coating of insulating material and saidcarbonaceous f layer overlapping one another so as to seal the saidplate, said coating of insulating material and said carbonaceous layeroverlapping one another so as to form-an insulating seal at thejunction. between the plate and the peripheral edges of the carbonaceouslayer, both said carbonaceous layer and said insulating coating beingapplied to said plate prior to assembly o f the plate in the cell, saidcarbonaceous layer forming one electrode of the cell, a zinc plateforming the other electrode the cell. and anv outer sealing skinenclosing said battery and uniting with said insulating coating whichforms a flux therefor. FRANK mmm

